18 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
The fault code is already on your display
Note it down before pressing reset — resetting clears the code immediately. How to read fault codes →
Tap any card for details
Your boiler has stopped working because it cannot accurately measure the temperature of the water being circulated to your radiators.
Your boiler has detected a problem with a temperature sensor inside the flue system, which stops the unit from operating to ensure it remains safe.
Your boiler is struggling because a sensor that monitors the temperature of the water returning to the system is failing, which prevents it from heating your home correctly.
Your boiler has detected that water is not flowing through the system correctly, which is preventing it from heating your home safely.
Your boiler has switched itself off because it has reached too high a temperature, likely due to trapped air or a blockage stopping water from circulating.
Your boiler has automatically shut down because it has detected that its internal water temperature has become dangerously high.
Your boiler has too much water in the system, which puts extra stress on the internal parts and may cause it to shut down for safety.
Your boiler has detected that there is not enough water in the system to operate safely, causing it to shut down temporarily.
Your boiler has detected that water isn't moving through the system properly, which is causing it to overheat and shut down for safety.
Your boiler started to heat up but the flame went out unexpectedly while it was running.
Your boiler has detected that the temperature of the gases leaving your flue is too high, so it has shut itself down to prevent any damage.
Your boiler has tried to ignite but failed to stay alight, which is often caused by a lack of gas supply or a blocked condensation pipe.
Your boiler has failed to light the flame needed to heat your water and home, and has safely shut down to prevent gas from building up.
Your boiler's fan is not spinning at the correct speed, which prevents the system from safely clearing exhaust fumes and starting the ignition process.
Your boiler has detected an issue with how it clears exhaust gases or brings in fresh air, preventing it from firing up for safety.
Your boiler is struggling to accurately measure the temperature of the water being heated for your taps and shower, so it has stopped producing hot water to prevent damage.
Your boiler has detected a flame signal when it should be turned off, so it has locked itself out to prevent a potential safety issue.
Your boiler has stopped working because the amount of water inside the system has dropped too low.
Not faults — these are normal operating states. Tap to expand.
Monthly cover means no unexpected bills when your boiler breaks down.
Affiliate links. We may earn a commission at no extra cost to you.
BoilerFaultCodes